1. Example of sequential spectral analysis during the tilt test.
Example of sequential spectral analysis during the tilt test. Boxes on the tachogram (A) indicate the three 5 min epochs (Ph1: basal rest supine; Ph2: onset of passive tilt and Ph3: end of passive tilt) when HRV parameters are calculated. Spectral analysis evidence of physiological prevalence of the vagal (HF) component in the supine position (B), and its decrease (with concomitant increase of the LF component) during the subsequent phases (C and D) of the study (HF, high frequency; HRV, heart rate variability; LF, low frequency; nu, normalised units). NTG, nitroglycerin; PSD, power spectral density; RR, interval between subsequent R waves.
Kristian Efremov et al. Open Heart 2014;1:e000063
©2014 by British Cardiovascular Society